Blind multiuser detection over highly dispersive CDMA channels

This paper addresses blind multiuser detection in a direct-sequence code-division multiple-access (DS-CDMA) network in presence of both multiple-access interference and intersymbol interference. In particular, it considers a DS-CDMA system where K out of N users are transmitting; the N admissible spreading codes are known, and so is the code of the user to be demodulated. The number of interferers, the signatures of a certain number, possibly all, of the interferers, and the channel impulse response of each active user are unknown. The spreading codes of the unknown interferers are determined via a procedure that exploits the knowledge of the set of admissible transmitted codes and of the known active codes. The procedure applies to both single and multiple receiving antennas. The performance assessment of a blind decorrelating detector, implemented by resorting to the proposed identification procedure, shows that it outperforms a plain subspace-based blind decorrelator for small sizes of the estimation sample.